Transistorized ignition system having an integrating circuit



Dec. 12, 1967 o. HUNTZINGER 3,357,416

TRANSISTORIZED IGNITION SYSTEM HAVING AN INTEGRATING CIRCUIT Filed Oct. 11, 1965 PICKUP & INTEGRATING I AMPLIFIER MULTIVIBRATOR I I VIBRATION SIGNAL FLUX lCAM ROTATION, DEGREES v w R E E P E G S W G H S I m G W T m o C l- I a R m N m m E EM R c m xw T L 0 m U P POINT OF VOLTAGE I A\" V EXTOR.

RISE CURVE OF CAM & CIRCUIT BREAKER POINTS CLOS ATTORNEY United States Patent 3,357,416 TRANSISTBRIZED IGNITION SYSTEM HAVING AN INTEGRATING CIRCUIT Gerald G. Hnntzinger, Anderson, Intl., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Oct. 11, 1965, Ser. No. 494,744 5 Ulaims. (Cl. 123148) ABSTRACT OF THE DISCLOSURE This invention relates to a transistorized ignition system of the type wherein the ignition synchronizing pulses are produced by a magnetic pulse generator. The pulses produced by the pulse generator are integrated in an integrating circuit comprising the parallel combination of two series resistors and the emitter-collector electrodes of a transistor device connected across the direct current potential line. The magnetic pulse generator pick-up coil is connected between the base electrode of the transistor and the junction between the two series connected resistors and an integrating capacitor is connected between the collector and base electrodes of the transistor. This circuit integrates the magnetic pulse generator output and supplies trigger signals to the remainder of the circuitry which are of substantially constant magnitude regardless of engine speed.

This invention relates to transistorized ignition systems for internal combustion engines and, more specifically, to transistorized ignition systems of the type wherein the ignition synchronizing potential pulses produced by a magnetic pulse generator are maintained substantially constant in amplitude with varying engine speeds by an integrating circuit arrangement.

With transistorized ignition systems for internal combustion engines, it is desirable to use a magnetic pulse generator comprising a simple permanent magnet and pick up coil arrangement which may be mounted in any standard type distributor in place of the conventional contact points. A unit of this type will produce potential pulses as each lobe of the breaker cam, driven in timed relationship with the engine, passes in close proximity to the magnetic assembly thereby varying the reluctance of the magnetic circuit.

The potential pulses produced by a magnetic pulse generator of this type are of a low amplitude at the slow rotational breaker cam speeds encountered during cranking, thereby necessitating a large amplification of the developed signal. The large amplification required renders the system extremely sensitive to spurious signals, produced by mechanical vibration and electrical transient impulses present in the power system, which may create ignition signals at unwanted times.

To substantially reduce or eliminate these disadvantages, the potential pulses developed in the pick up coil of the magnetic pulse generator, which are proportional to the time rate of change of magnetic flux linking the coil winding, may be integrated by an integrating circuit arrangement. With this arrangement, the integrated output signal is substantially constant in amplitude regardless of engine speed.

By integrating the potential signal pulses generated by the magnetic pulse generator, spurious signals generated by vibrations of the pulse generator and transients present in the power system are greatly attenuated as these signals are of a much higher frequency than the generated signals.

It has been found that the wave form of the integrated signal is similar in phase and timing to the motion of a conventional circuit breaker riding the cam. Representative curves are set forth in FIGURES 4c and 4d, respectively.

Therefore, the integrated signal may be used to trigger a transistor ignition system to produce ignition pulses which are synchronized with the engine in the same manner as those produced by conventional breaker points which are operated to open and close by the breaker cam.

It is, therefore, an object of this invention to provide an improved transistorized ignition system for internal combustion engines.

It is another object of this invention to provide an improved transistorized ignition system for internal combustion engines of the type wherein the ignition synchronizing potential pulses are produced by a magnetic pulse generator.

It is a further object of this invention to provide an improved transistorized ignition system for internal combustion engines wherein the ignition synchronizing potential pulses produced by a magnetic pulse generator are maintained substantially constant in amplitude with varying engine speeds by an integrating circuit arrangement.

In accordance with this invention, an improved transistorized ignition system for internal combustion engines is provided wherein the ignition synchronizing potential signal pulses produced by a magnetic pulse generator are maintained substantially constant in amplitude with varying engine speeds by an integrating circuit arrangement and applied to associated transistorized circuitry which operates to interrupt the current flow through the primary winding of an ignition coil in timed relationship with the engine.

For a better understanding of the present invention together with additional objects, advantages and features thereof, reference is made to the following description and accompanying drawing in which:

FIGURE 1 is a schematic perspective view of a magnetic ignition synchronizing potential pulse generator satisfactory for use with this invention,

FIGURE 2 schematically sets forth an integrating circuit arrangement which may be used in combination with the magnetic ignition synchronizing potential pulse generator of FIGURE 1,

FIGURE 3 schematically sets forth the integrating circuit arrangement shown in FIGURE 2 in combination with a transistorized ignition system for internal combustion engines, and,

FIGURES 4a through 4d are a set of curves useful in understanding the operation of the circuits schematically set forth in FIGURES 2 and 3.

Throughout the several figures of the drawing, like elements have been given like characters of reference.

Referring to FIGURES 1, a magnetic pulse generator for producing ignition synchronizing potential pulses in timed relationship with an associated internal combustion engine is schematically set forth. The magnetic circuit of this type generator includes a permanent magnet 10, an associated pole piece of magnetic material 12 and the breaker cam 14 of a standard automotive type distributor, herein shown to have six lobes for use with a six cylinder internal combustion engine. The magnetic flux in this magnetic circuit varies in a manner as shown in FIGURE 4a, the greater magnitudes occurring as the lobes of breaker cam 14 pass in close proximity to pole piece 12 as breaker cam 14 is rotated by and in timed relationship with the associated internal combustion engine in a manner well known in the art. The varying flux density present in the magnetic circuit induces in pick up coil 16 an alternating current potential wave form, the pulses of which occur in timed relation with the engine as shown in FIGURE 4b. It may be noted in FIGURE 4b that the positive and negative excursions of this induced alternating current wave form change in amplitude with rotational speed because of the different rate of change of magnetic flux which links pick up coil 16.

To integrate the ignition synchronizing potential pulses produced by the magnetic pulse generator of FIGURE 1, a potential integrating arrangement is required. One example of a satisfactory integrating arrangement is schematically set forth in FIGURE 2. A type PNP integrating transistor device having the usual base 21, emitter 22 and collector 23 electrodes in combination with 'a capacitor 26 connected across the base 21 and collector 23 electrodes may be employed. The specific connections and operation of this integrating arrangement will be described in detail in reference to FIGURE 3.

FIGURE 3 schematically sets forth the magnetic ignition synchronizing potential pulse generator of FIGURE 1 and the integrating circuit arrangement of FIGURE 2 in combination with an ignition system for an internal combustion engine wherein the current supplied by a direct current potential source, which may be a battery 15, flowing through the primary winding 34 of an ignition coil 36 and the'emitter 42 and collector 43 electrodes of a normally conducting type PNP transistor switching device 40, in series, is periodically interrupted in timed relationship with the engine by triggering transistor switching device 40 to non-conduction in timed relationship with the engine.

To trigger transistor switching device 40 to non-conduction in timed relationship with the engine, it isnecessary to provide circuitry which is responsive to the integrated ignition synchronizing pulses. This circuitry may be a conventional monostable multivibrator circuit comprising transistors 44 and 46 and the associated circuitry.

As is well. known in the art, monostable multivibrators have a stable state of operation and may be triggered to analternate state of operation by an electrical signal. These devices remain in the alternate state of operation for a period of time, as determined by the associated circuitry, at the conclusion of which they spontaneously return to the stable state of operation.

Upon the closure of switch 30 of FIGURE 3, which may be a conventional automotive type ignition switch, to either the run terminal 31 or the crank terminal 32, the electrical potential appearing on line 48 is of a positive polarity and the electrical potential appearing on line 50 is of a negative polarity. Therefore, line 48 will hereinafter be referred to as the positive potential line and line 50 will hereinafter be referred to as the negative potential line.

The emitter 22 and collector 23 electrodes of type PNP integrating transistor 20 are connected across the direct current supply potential source, battery 15, through positive potential line 48 and switch 39 and negative potential line 50, respectively. Connected in this manner, the emitter 22 and collector 23 electrodes of integrating transistor 20 are forward poled. That is, polarized in such a manner that emitter to collector current will flow in response to a control current which is made to flow from the emitter to base electrodes.

A first resistor 24 and a second resistor are also connected in series across the direct current potential source, battery 15, through positive potential line 48, switch and negative potential line 50.

A capacitor 26 is connected across the base 21 and collector 23 electrodes of integrating transistor 20.

Pick up coil 16 of the magnetic pulse generator of FIG- URE 1 is connected in series between the base electrode 21 of integrating transistor 20 and junction 18 between series connected resistors 24 and 25.

The emitter electrodes and collector electrodes of transistors 44 and 46 of the multivibrator circuit are connected to positive potential line 48 through diode 60 and resistor 58 and negative potential line 50 through resistors 62 and 73, respectively. Therefore, the emitter-collector electrode circuit of type PNP transistors 44 and 46 are forward poled.

The base electrode of transistor 44 is connected to junction 52 between resistor 28 and the collector electrode 23 of integrating transistor 20 through resistor 53.

The base electrode of transistor 46 is connected to the junction between resistor 62 and the collector electrode of transistor 44 through capacitor 56 and to negative potential line 50 through resistor 54.

The emitter electrode 42 and the collector electrode 43 of switching transistor 40 is connected to positive potential line 48 and negative potential line 50, respectively. Therefore, the emitter-collector electrode circuit of type PNP switching transistor 40 is forward poled. The base electrode 41 of switching transistor 40 is connected to junction 64 between diode 60 and resistor 58.

In operation, with switch 30 closed to either the crank terminal 32' or the run terminal 31, the system potential appears across lines 48 and 50.

Resistors 24 and 25 are arranged to have relative values such that the potential appearing at junction 18 is of a polarity more negative than the potential applied to the emitter electrode 22, a condition which satisfies the baseemitter bias requirement for base-emitter current conduction through a type PNP transistor, therefore, integrating transistor 20 is normally conducting.

As the base electrode of transistor 46 is connected to negative potential line 50 through resistor 54, the potential upon the base electrode is of a polarity more negative than the potential upon the emitter electrode thereof. As this condition satisfies the base-emitter bias require mens for the flow of base-emitter current flow through a type PNP transistor, transistor 46 is normaily conducting.

With integrating transistor 20 conducting, the potentiai appearing at junction 52 is of a positive polarity and is applied to the base electrode of transistor 44 through resistor 53. The emitter electrode of transistor 44 is returned to positive potential line 48 through diode 60 and resistor 58. The value of resistor 28 is arranged to be such that the potential at junction 52 is more positive than the potential of the emitter elecrode of transistor 44. As this condition does not satisfy the base-emitter bias requirements for base'emitter current flow through a type PNP transistor, transistor 44 is normally not conducting.

During the normally not conducting condition of transistor 44, capacitor 56 is charged nearly to line potential by current flowing from positive line 48 through resistor 58, diode 60, the emitter-base junction of transistor 46, capacitor 56 and resistor 62 to negative line 50.

Conducting transistor 46 also establishes a potential at junction 64 which is of a polarity which is negative in re spect to line 48. As this potential is applied to the base electrode of forward poled switching transistor 40, a condition which satisfies the base-emitter bias requirement for base-emitter current conduction through a type PNP transistor, switching transistor 40 is also normally conducting and the primary winding 34 of ignition coil 36 is being emergized.

As breaker cam 14 is driven by and in timed relation with the engine, the variable flux density of the magnetic circuit of the magneti pulse generator, as shown in FIGURE 4a, induces in pick up coil 16 an alternating current wave form as shown in FIGURE 4b, the alternating current pulses being produced in timed relationship with the engine. The alternating current wave form of FIGURE 4b is integrated by the circuitry schematically set forth in FIGURE 2 and appears at the output terminals thereof as an integrated voltage wave form substantially as shown in FIGURE 40. Comparing the curve of FIGURE 40 with that of FIGURE 4d, which is a graph of motion of a conventional circuit breaker riding the cam. it is seen that these curves nearly approximate each other, therefore, the magnetic pulse generator hereinabove described in combination with the integrating circuitry may be substituted in a standard type distributor for the breaker points.

With each ignition synchronizing potential pulse developed in pick up coil 16 of the magnetic pulse generator, a current flows, the magnitude of which is dependent upon the magnitude of this potential and the circuit resistance which is essentially the parallel value of resistors 24 and 25 plus the resistance of pick up coil winding 16. As the current gain of integrating transistor 20 is high, a large proportion of this current flows into capacitor 26, which is connected between the base electrode 21 and the collector electrode 23 of integrating transistor 20. The potential developed across capacitor 26 is the integral of the current flowing through the capacitor as produced by the potential pulses induced in pick up coil 16. The output potential, which may be taken across the emitter 22 and collector 23 electrodes of integrating transistor 20, is nearly equal to the potential appearing across capacitor 26, therefore, the output potential is approximately equal to the integral of the input potential induced in pick up coil 16 and is of a wave form substantially as shown in FIGURE 4c.

By taking the output signal from across integrating transistor 20 rather than across the collector resistor 28 thereof, the effects of spurious signals, such as the vibration signals shown in FIGURES 4a, 4b and 4c, and transient pulses in the power supply are drastically attenuated. These spurious signals are first attenuated by resistors 24 and 2S and appear at the base electrode 21 of integrat ing transistor 20 in reduced magnitude. As these spurious signals are in series with the ignition pulses produced by the pulse generator, they are integrated by the integrating circuit, and, since they are usually of a higher frequency than the generated signal pulses, the integration process further reduces the magnitude thereof.

As the integrated potential goes more positive as shown in FIGURE 4c, integrating transistor begins to conduct less because of the reverse base bias and the polarity of the potential at junction 52 begins to go more negative until of sufiicient magnitude to trigger transistor 44 to conduction.

'Upon the conduction of transistor 44, the potential of the collector electrode changes in a positive direction. Capacitor 56, which has been previously charged to a negative potential at the collector of transistor 44 and positive at the base of transistor 46, now applies the positive going signal from the collector of transistor 44 to the base of transistor 46. With this condition, transistor 46 is quickly cut-off and the potential appearing at junction 64 goes positive. The positive polarity potential appearing at junction 64 biases the base of switching transistor 40 to non-conduction, thereby interrupting the energizing circuit for the primary winding 34 of ignition coil 36. The resulting collapsing magnetic field induces in secondary coil 66 thereof a high potential which is distributed to the spark plugs of the internal combustion engine in a manner well known in the art.

With transistor 46 not conducting, the potential at junction 68 goes negative and this negative potential is applied to the base electrode of transistor 44 through line 70 and resistor 72. As this potential is of the proper polarity to forward base bias a type PNP transistor, it tends to hold transistor device 44 conducting.

When transistor 44 conducts, capacitor 56 discharges through resistor 54, battery 15, the run or crank switch contacts 31 or 32, line 48, resistor 58, diode 60 and the emitter-collector electrodes of transistor 44. Upon the completion of the discharge of capacitor 56, the negative polarity base bias potential at junction 74 is again applied to the base electrode of forward poled transistor 46. As this condition satisfies the base-emitter bias requirement for base-emitter current conduction through a type PNP transistor, transistor 46 again conducts. With transistor 45 conducting, the potential at junction 68 goes positive removing the negative bias applied to the base electrode of transistor 44 through line 70 and resistor 72. Thereafter, transistor 44 may be base biased to nonconduction by the positive going signal appearing at junction 52. This action then permits capacitor 56 to be recharged as previously described in preparation for the next synchronizing pulse.

Conducting transistor 46 also establishes a negative polarity potential at junction 64 which, when applied to the base electrode of switching transistor 40 biases this device to conduction thereby reestablishing the energizing circuit for the primary coil 34 of ignition coil 36 and the circuit is prepared to receive the next ignition potential pulse produced by the magnetic pulse generator whereupon the operation just described is repeated.

As the ignition pulses are produced by the magnetic pulse generator in timed relationship with the engine, switching transistor 40 is triggered ofi" to interrupt the energizing circuit for primary winding 34 of ignition coil 36 in timed relation with the engine thereby producing the properly timed high voltage pulses for firing the engine spark plugs in a manner well known in the art.

While specific transistor types have been described in this specification, it is to be specifically understood that alternate types may be employed.

While a preferred embodiment of the present invention has been shown and described, it will be obvious to those skilled in the art that various modifications and substitutions may be made without departing from the spirit of the invention which it to be limited only within the scope of the appended claims.

What is claimed is as follows:

1. In an ignition system for an internal combustion engine of the type wherein the current supplied by a direct current potential source flowing through the primary winding of an ignition coil and the emitter-collector electrodes of a normally conducting transistor switching device in series is periodically interrupted in timed relationship with said engine by triggering said transistor switching device to nonconduction in timed relationship with said engine, the combination with said direct current potential source, ignition coil and transistor switching device of a magnetic pulse generator means for producing ignition synchronizing potential pulses in timed relationship with said engine, means for integrating said ignition synchronizing potential pulses and means responsive to said integrated ignition synchronizing potential pulses for triggering said transistor switching device to nonconduction in timed relationship with said engine.

2. In an ignition system for an internal combustion engine of the type wherein the current supplied by a direct current potential source flowing through the primary winding of an ignition coil and the emittter-collector electrodes of a normally conducting transistor switching device in series is periodically interrupted in timed relationship with said engine by triggering said transistor switching device to nonconduction in timed relationship with said engine, the combination with said direct current potential source, ignition coil and transistor switching device of a magnetic pulse generator means for producing ignition synchronizing potential pulses in timed relationship with said engine, an integrating semiconductor device having a control electrode and two current carrying electrodes, a capacitor, means for connecting said current carrying electrodes of said integrating semiconductor device across said direct current potential source and forward poled, means for connecting said capacitor across said control electrode and one of said current carrying electrodes of said integrating semiconductor device, means for applying said ignition synchronizing potential pulses across said control electrode and one of said current carrying electrodes of said integrating semiconductor device and means responsive to the potential appearing across said integrating semiconductor device for triggering said transistor device to nonconduction in timed relationship with said engine.

3. In an ignition system for an internal combustion engine of the type wherein the current supplied by a direct current potential source flowing through the primary winding of an ignition coil and the emitter-collector electrodes of a normally conducting transistor switching device in series is periodically interrupted in timed relationship with said engine by triggering said transistor switching device to nonconduction in timed relationship with said engine, the combination with said direct current potential source, ignition coil and transistor switching device of a magnetic pulse generator means for producing ignition synchronizing potential pulses in timed relationship with said engine, an integrating transistor device having base, emitter and collector electrodes, means for connecting said emitter and collector electrodes of said integrating transistor device across said direct currentrpo-tential source and forward poled, a capacitor, means for connecting said capacitor across said base and collector electrodes of said integrating transistor device, means for applying said ignition synchronizing potential pulses across said base and collector electrodes of said integrating transistor device and means responsive to the potential apprearing across said integrating transistor for triggering said transistor switching device to nonconduction in timed relationship with said engine.

4. In an ignition system for an internal combustion engine of the type wherein the current supplied by a direct current potential source flowing through the primary winding of an ignition coil and the emitter-collector electrodes of a normally conducting transistor switching device in series is periodically interrupted in timed relationship with said engine by triggering said transistor switching device to nonconduction in timed relationship with said engine, the combination with said direct current potential source, ignition coil and transistor switching device of a magnetic pulse generator means including a pick up coil for producing ignition synchronizing potential pulses in timed relationship with said engine, an integrating transistor device having base, emitter and collector electrodes, a first resistor, a second resistor, a capacitor, means for connecting said emitter and collector electrodes of said integrating transistor device across said direct current potential source and forward poled, means for connecting said first and second resistors in series across said direct current potential source, means for connecting said capacitor across said base and collector electrodes of said integrating transistor device, means for connecting said pick up coil in series between said base electrode of said integrating transistor device and the junction between said first and second resistors and means responsive to the potential appearing across said integrating transistor device for triggering said transistor switching device to nonconduction in timed relationship with said engine.

5. In an ignitionsystem for an internal combustion engine of the type wherein the current supplied by a direct current potential source flowing through the primary winding of an ignition coil and the emitter-collector electrodes of a normally conducting transistor switching device in series is periodically interrupted in timed relationship with said engine by base biasing said transistor switching device to nonconduction in timed relationship with said engine, the combination with said direct current potential source, ignition coil and transistor switching device of a magnetic pulse generator means including a pick up coil for producing ignition synchronizing potential pulses in timed relationship with said engine, an integrating transistor device having base, emitter and collector electrodes, a first resistor, a second resistor, a capacitor, means for connecting said emitter and collector electrodes of said integrating transistor device across said direct current potential source and forward poled, means for connecting said first and second resistors in series across said direct current potential source, means for connecting said capacitor across said base and collector electrodes of said integrating transistor device, means for connecting said pick up coil in series between said base electrode of said integrating transistor device and the junction between said first and second resistors, a monostable multivibrator circuit having a stable and an alternate state of operation and at least an input terminal and an output terminal for triggering said transistor switching device to nonconduction when inrsaid alternate state of operation, means for connecting said output terminal to said base electrode of said transistor switching device and means for applying the potential appearing across said integrating transistor device to said input terminal of said monosta-ble multivibrator circuit.

References Cited UNITED STATES PATENTS LAURENCE M. GOODRIDGE, Primary Examiner. 

1. IN AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE OF THE TYPE WHEREIN THE CURRENT SUPPLIED BY A DIRECT CURRENT POTENTIAL SOURCE FLOWING THROUGH THE PRIMARY WINDING OF AN IGNITION COIL AND THE EMITTER-COLLECTOR ELECTRODES OF A NORMALLY CONDUCTING TRANSISTOR SWITCHING DEVICE IN SERIES IS PERIODICALLY INTERRUPTED IN TIMED RELATIONSHIP WITH SAID ENGINE BY TRIGGERING SAID TRANSISTOR SWITCHING DEVICE TO NONCONDUCTION IN TIMED RELATIONSHIP WITH SAID ENGINE, THE COMBINATION WITH SAID DIRECT CURRENT POTENTIAL SOURCE, IGNITION COIL AND TRANSISTOR SWITCHING DEVICE OF A MAGNETIC PULSE GENERATOR MEANS FOR PRODUCING IGNITION SYNCHRONIZING POTENTIAL PULSES IN TIMED RELATIONSHIP WITH SAID ENGINE, MEANS FOR INTEGRATING SAID IGNITION SYNCHRONIZING POTENTIAL PULSES AND MEANS RESPONSIVE TO SAID INTEGRATED IGNITION SYNCHRONIZING POTENTIAL PULSES FOR TRIGGERING SAID TRANSISTOR SWITCHING DEVICE TO NONCONDUCTION IN TIMED RELATIONSHIP WITH THE ENGINE. 